Using forward end-sweep to reduce transonic cantilevered stator losses to improve compressor performance

ABSTRACT The complicated flows in a transonic cantilevered stator would cause serious aerodynamic losses and reducing these losses would contribute much to improving the overall aerodynamic performance of a compressor. The paper conducts an overview study of the potential aerodynamic losses in a transonic cantilevered stator and presents a systematic numerical study for the effects of forward end sweep on reducing aerodynamic losses. A 2-D stator blade is used to throw light upon the physical mechanism of the forward end sweep on reducing the losses. At the casing region, forward end sweep has led to a redistribution of the blade load along the chordwise direction, higher in the front part and lower in the rear part. This result leads to a lower pressure gradient from the 30% chord location to the trailing edge and can be beneficial for the reduction of the corner separation. At the hub region, on one aspect, forward end sweep reduces both the peak Mach number and the size of the high-Ma region of the blade suction surface, thus decreasing the shock loss near the hub. On the other aspect, it also reduces the peak load and the strength of the leakage vortex, therefore alleviating the flow blockages. Simultaneously, the forward end sweep is applied to a commercial and high-performance multistage compressor to further validate its feasibility. When the technique is applied to the transonic first four stator rows, an improvement of adiabatic efficiency is achieved by ∼ 0.85% and the compressor stable operating range is slightly increased. The results suggest that the forward end-swept transonic cantilevered stators have a significant potential for reducing the stator losses. They would provide guidelines to advance the cantilevered stator design and further improve the compressor aerodynamic performance. Abbreviations: h, stagnation enthalpy; , stagnation pressure; p, static pressure; U, blade rotational speed at tip; V, velocity; , non-dimensional wall distance; , total pressure loss coefficient; , flow coefficient (Vx/U); , stage load coefficient (Δh/U2); , adiabatic efficiency; , total pressure ratio; in, inlet; out, outlet; LE/TE, leading/trailing edge; PS/SS, pressure/suction surface

[1]  Usama Umer,et al.  Performance Evaluation of Tandem Bladed Centrifugal Compressor , 2014 .

[2]  R. P. Dring,et al.  Axial Compressor Stator Aerodynamics , 1985 .

[3]  S. L. Puterbaugh,et al.  Control of Shock Structure and Secondary Flow Field Inside Transonic Compressor Rotors Through Aerodynamic Sweep , 1998 .

[4]  Volker Gümmer,et al.  Using Sweep and Dihedral to Control Three-Dimensional Flow in Transonic Stators of Axial Compressors , 2000 .

[5]  H. Schulz,et al.  Experimental Investigation of the Three-Dimensional Flow in an Annular Compressor Cascade , 1988 .

[6]  Leroy H. Smith,et al.  Sweep and Dihedral Effects in Axial-Flow Turbomachinery , 1963 .

[7]  Howard P. Hodson,et al.  Aerothermal Investigations of Tip Leakage Flow in Axial Flow Turbines-Part II: Effect of Relative Casing Motion , 2009 .

[8]  Peter Wood,et al.  Effect of the Stator Hub Configuration and Stage Design Parameters on Aerodynamic Loss in Axial Compressors , 2014 .

[9]  Nicholas A. Cumpsty,et al.  The Use of Sweep and Dihedral in Multistage Axial Flow Compressor Blading: Part II — Low and High Speed Designs and Test Verification , 2002 .

[10]  Martin Lange,et al.  An Experimental Verification of a New Design for Cantilevered Stators With Large Hub Clearances , 2013 .

[11]  Roy F Behlke,et al.  Bowed stators : An example of CFD applied to improve multistage compressor efficiency , 1997 .

[12]  Nicholas A. Cumpsty,et al.  The Use of Sweep and Dihedral in Multistage Axial Flow Compressor Blading—Part I: University Research and Methods Development , 2002 .

[13]  Jens Friedrichs,et al.  Effect of stator design on stator boundary layer flow in a highly loaded single-stage axial-flow low-speed compressor , 2001 .

[14]  Michael D. Hathaway,et al.  Laser anemometer measurements in a transonic axial-flow fan rotor , 1989 .

[15]  T. H. Okiishi,et al.  Stator Endwall Leading-Edge Sweep and Hub Shroud Influence on Compressor Performance , 1986 .

[16]  Aspi Rustom Wadia,et al.  Inner Workings of Aerodynamic Sweep , 1997 .

[17]  Chunill Hah,et al.  THE IMPACT OF FORWARD SWEEP ON TIP CLEARANCE FLOWS IN TRANSONIC COMPRESSORS , 2004 .

[18]  Paolo Boncinelli,et al.  Complementary Use of CFD and Experimental Measurements to Assess the Impact of Shrouded and Cantilevered Stators in Axial Compressors , 1999 .

[19]  Ernesto Benini,et al.  On the Aerodynamics of Swept and Leaned Transonic Compressor Rotors , 2006 .

[20]  Mahesh K. Varpe,et al.  Numerical Investigation of the Effect of Moving Endwall and Tip Clearance on the Losses in a Low Speed Axial Flow Compressor Cascade , 2013 .

[21]  Martin Lange,et al.  An Experimental Verification of a New Design for Cantilevered Stators With Large Hub Clearances , 2012 .

[22]  Weixiong Chen,et al.  Effects of tip clearance size on the performance and tip leakage vortex in dual-rows counter-rotating compressor , 2015 .

[23]  Howard P. Hodson,et al.  Three-Dimensional Flows and Loss Reduction in Axial Compressors , 1986 .

[24]  J. A. Storer,et al.  Tip Leakage Flow in Axial Compressors , 1990 .

[25]  F. A. E. Breugelmans,et al.  Comparison of Sweep and Dihedral Effects on Compressor Cascade Performance , 1997 .

[26]  John D. Denton,et al.  The exploitation of three-dimensional flow in turbomachinery design , 1998 .

[27]  John D. Denton,et al.  The Effects of Lean and Sweep on Transonic Fan Performance , 2002 .